Over 10 million metric tons of oxo-chemicals are consumed annually for the synthesis of a wide array of industrial and consumer products, including plasticizers, antifreeze products, aircraft and runway de-icing products, solvents, hydraulic fluids, paints, lubricants, cosmetics, fine chemicals, and pharmaceuticals. Currently, the dominant technology for C3-C15 oxo-chemical production is hydroformylation, also known as oxo-synthesis or the oxo-process. This catalytic chemical process involves the addition of a formyl group and a hydrogen atom to an olefin (a hydrocarbon with a carbon-carbon double bond) under high temperature and pressure conditions. Propylene-derived C4 oxo-chemicals account for nearly 73% of the worldwide consumption of oxo-chemicals. The production of C4 oxo-chemicals requires propylene as starting material, making the process not sustainable. The substantial energy costs for maintaining the high temperature and pressure conditions necessary in the current manufacturing process limits the overall energy efficiency and is thus deemed environmentally unfriendly.
Therefore, new methods for producing C4 oxo-chemicals using biological conversion of renewable resources such as sugar and cellulose have been developed and more recently also deployed. Among other advantages, it should be noted that biomass-derived substrates fix CO2 naturally, leading to a carbon neutral oxo-chemical production process.
Another approach to producing oxo-chemicals involves the metabolic engineering of microorganisms to produce chemicals of interest. For example, various Clostridium species (without genetic alteration) may be cultured to produce 1-butanol. However, all or almost all of those known processes require separation of the 1-butanol and so have high recovery cost. Selected strains of Clostridium have been metabolically engineered to enhance the expression of 1-butanol over other products, however the lack of genetic tools available for regulating the metabolic pathways of Clostridium has impeded progress in that avenue. To circumvent the difficulties associated with metabolic engineering of Clostridium, various alternative microbial species have been considered that are better understood and more easily modified, including Escherichia coli and Saccharomyces cerevisiae, among others.
Notwithstanding the difficulties with Clostridium, Kouba et al. teach in U.S. Pat. App. No. 2012/0209021, incorporated herein by reference in its entirety, a method of producing n-butyraldehyde using recombinant solventogenic bacteria and recombinant microorganisms. Here, Kouba et al. describe a two-step method involving recombinant Clostridium in which (1) the recombinant bacterium is cultured and (2) the resulting n-butyraldehyde is isolated from the culture medium upon termination of fermentation. While such approach is at least conceptually desirable, several drawbacks nevertheless remain. Among other things, the yield of n-butyraldehyde in the system of Kouba is relatively low.
Thus, even though various systems and methods of production of n-butyraldehyde are known in the art, all or almost all of them suffer from one or more drawbacks. Consequently, there is still a need to provide improved systems and methods for microbial production of n-butyraldehyde.